Apparatus for filling and compacting a mix into a form for making precast elements

ABSTRACT

Mass production of small precast concrete elements is improved with regard to uniformity of dimensions and of concrete compactability by a novel method and apparatus for filling the concrete mix into the form and compacting the mix in the form. According to the invention the form is evenly filled with a premetered quantity of concrete mix and any surplus due to inhomogeneities in the mix is removed during compacting of the concrete.

United States Patent Schneider et al.

[151 3,655,318 [451 Apr. 11, 1972 APPARATUS FOR FILLINGAND COMPA" f 'G A MIX INTO A FORM FOR MAKING PRECAST ELEMENTS Wolfgang Schneider, Mushardweg 8;

Klaus Schneider, Feldweg l8, both of 2150 Buxtehude, Germany Filed: Nov. 21, 1969 Appl. No.: 878,682

Inventors:

Foreign Application Priority Data Nov. 21, 1968 Germany ..P I8 10 I285 May 22, 1969 Gennany........... ....P 19 26 263.6 June 7, 1969 Germany ..P 19 28 967.9

US. Cl ..425/2l8, 425/256, 425/346 Int. Cl ..B28b 13/02 FieldoiSearch ..25/l03,83,4l T,4IJ,4I R, 25/4l D, 41 E, 104; 264/69, 71, 333

[56] References Cited UNITED STATES PATENTS [905,975 4/ I933 Thomas ..25/4 I D FOREIGN PATENTS 0R APPLICATIONS 22,067 1896 Great Britain ..25/4l T Primary Examiner-J. Spencer Overholser Assistant Examiner-David S. Safran Attomey-Young & Thompson [57] ABSTRACT Mass production of small precast concrete elements is improved with regard to uniformity of dimensions and of concrete compactability by a novel method and apparatus for filling the concrete mix into the form and compacting the mix in the form. According to the invention the form is evenly filled with a premetered quantity of concrete mix and any scrplus due to inhomogeneities in the mix is removed during compacting of the concrete.

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lnrenfors Hrrvs- PATENTEDAPR 1 1 are 3 fJWN APPARATUS FOR FILLING AND COMPACTING A MIX INTO A FORM FOR MAKING PRECAST ELEMENTS The invention relates to a method of mass producing precast concrete elements in substantially automatically operating casting equipment. The precast concrete elements contemplated in the context of the present invention are primarily understood to be concrete paving setts, but they may also be paving flags, slabs for footways, concrete blocks for lining the banks of waterways and similar precast concrete elements. Frequently such precast concrete elements, particularly paving setts, are required to comply with very stringent qualitative specifications. These relate firstly to the quality of the concrete itself and secondly to the maintenance of prescribed dimensions within strict tolerance limits. Since the side faces of such precast elements are usually shaped by the sides of the form in which they are produced, cross-sectional accuracy is readily achieved. However, the height of the elements, which is determined by the level to which the form is filled, is usually more difficult to keep constant because the tops of the forms are usually open.

The forms normally used for the mass production of such precast concrete elements are large frames divided into a plurality of separate compartments. in conventional casting equipment these compartments are filled from above from a filling carriage which usually has the form of a box with an open top and an open bottom. Irrespective of the level to which the compartments are to be filled, the filling box is charged to capacity with a concrete mix obtained from a hopper located on one side of the form and the box containing the mix is traversed across the form. The traverse of the box in one direction ends when the leading edge of the box reaches the far end of the compartmented form. Since the leading end of the box first crosses the edge of the form adjacent the hopper, the compartments along this edge of the form are filled first, whereas the remoter compartments of the form are at first only partially filled. By repeatedly traversing the filling box to and fro across the width of the form, all the compartments are eventually filled. Owing to the repeated traversing motion of the filling box, the mix in those parts of the form which are nearer the hopper is already partly compacted by the weight of the superimposed mix which is pushed along in the traversing box, whereas the mix received into the remoter parts of the form remains fairly loose. Although the described procedure may lead to an even filling of all the compartments, the quality of the precast elements thus obtained is not uniform because of differences in their degree of precompactron.

Difficulties also arise in the production of precast concrete elements because concrete is not a homogeneous mass. The use of sand and gravel of different screen sizes leads to the mix in the several compartments reacting differently to precom' paction, notwithstanding that all the compaflments may have been very evenly filled. These differences in quality are accentuated in conventional casting equipment, and by the production techniques that are employed. The same filling level and a uniformly controlled degree ofcompaction in all the compartments of the form can be only incompletely achieved. It therefore turns out that the heights of the precast compacted setts are different.

It is the object of the present invention to provide a method of producing precast concrete elements, which will permit the height of the finished precast elements, which depends upon the filling level in the compartments of a multiple form, to be accurately maintained within narrow tolerance limits. The precision which in this respect the proposed method sets out to achieve is intended to be sufiicient to permit say precast concrete setts or slabs to be cast edge-up that is to say in a position in which the filling level of the compartments determines a dimension which is critical from the point of view of laying a satisfactory paving. Another object of the invention is to provide a method in which not only the dimension determined by the filling level can be precisely maintained within given tolerance limits, but which also permits the compaction of the concrete in the several compartments of a multiple form to be more uniform than is possible to achieve by conventional methods in conventional equipment, and which thereby enables elements to be produced which besides being dimensionally accurate are also of very uniform quality. Finally it is an object of the invention to provide equipment in which the proposed method can be performed.

For achieving these objects the invention proposes a method of producing precast concrete elements in a form divided into a plurality of separate compartments, the top of the form fitting flush into an opening in a table top and the compartments of the form being filled with an exactly metered volume of concrete mix which is conveyed from a feeding station horizontally on the table top to the upwardly open form and thus filled into the form wherein the concrete mix is compacted and from which any excess filled into the form is abstracted, the compacted blanks of the precast elements being finally removed from the form, said method consisting in sweeping the concrete mix during the process of filling across the open top of the form onto that part of the table top which extends beyond the far end of the form whilst at the same time displacing the mix horizontally sideways at right angles to the direction of sweep, causing some of the concrete to drop into the fonn, and in then sweeping the remainder of the concrete mix back across the open top of the form and reversing the direction of horizontal sideways displacement during the return sweep.

In a preferred development of this method it is proposed, during the first part of the sweep of the concrete mix from the feeding station across the form, to drop the major part of the mix into the form by imparting short fore and aft reciprocating motions to the mix, the amplitude of said reciprocations being only a fraction of the length of the form in the direction of reciprocation, the remainder of the concrete mix being distributed between the compartments of the form by major sweeps of the mix along the length of the table in or contrary to the initial direction of sweep, accompanied by simultaneous displacements in the crosswise directions.

The method according to the invention improves the unifonnity of distribution of the mix to such an extent that during a following compaction there are substantially no perceptible differences between parts of the form which are first traversed by the filling box and the remoter parts of the form, differences which could not in the past be avoided. Any remaining irregularities which may arise as a result of fluctuations in the composition of the concrete mix are levelled out in the method according to the invention because any excess that may have been filled into the compartments of the form is abstracted during the process of compaction.

This latter step of the method is performed by using a ram which can be moved into a position vertically above the form, the pressing surface of said ram being subdivided in conformity with the subdivision into compartments of the form, and consisting of a plurality of compacting plates each fitted with means for the reception of excess material that may be present in the compartments, said means consisting of a downward extension on each compacting plate provided with an opening in its bottom end communicating with a receiving space above. Preferably the extension has the form of a downwardly tapering truncated hollow cone of which the wall thickness likewise tapers to the opening in the bottom end of the cone. According to another feature of the invention the cross section of the opening converges from the bottom sharp-edged end of the extension to a throat located below the level of the compacting plate and then diverges again in the upward direction.

The equipment the invention provides for performing the method comprises a frame-like form fitted from below flush into a table top which a filling box is adapted to traverse starting from a feeding and metering station for the concrete mix on one side of the form, said table extending a distance beyond the other side of the form that is at least equal to the length of the box. Preferably the filling box is divided into three sections of which the centre section consists of a funnel which downwardly ends with clearance above the table top, whereas the sections at each end of the box are providing with deflecting means which make sliding contact with the table top.

Other advantages and features of the invention that are claimed in the claims will be understood from the following particular and illustrative description of the proposed method and equipment used for performing the method, in which reference will be made to the accompanying drawings wherein F 165. 1a b to 50 b schematically show an embodiment of equipment according to the invention in five different operational phases, each phase being illustrated in a part sectional side elevation (a) and a view in plan (b) of the equipment,

FIG. 6 is the filling carriage, in plan,

FIG. 7 is a section taken on the line 7 7 in FIG. 6,

FIG. Sis a section taken on the line 8 8 in FIG. 6,

FIGS. 9 and 10 are two different sets of deflecting devices for use in a filling box according to the invention.

FIGS. 11a, 11b, 12a, to l2c,l3a, 13b and 14a, 14b are views of different embodiments of means according to the invention for abstracting an excess of material from the filled compartments of the form, and

H68. 15 to 19 illustrate consecutives working phases during compaction in equipment provided with abstracting devices as illustrated in FIGS. 11 to 14.

Referring first to FIG. 1 the proposed equipment comprises an upwardly open frame-like form 10 which is subdivided into a number of identical compartments. The top edge of the form 10 is set into an opening in a table 12 flush with the table top which continues on both sides of the form. The table 12 stands on a supporting structure not shown in the drawing. Rails 14 are affixed to the longitudinal edges of the table 12. The form 10 itself is mounted on a smaller table 16 below which is a conventional vibrator 18. Above the form a ram 20 can be raised and lowered by a hydraulic ram cylinder 22. The ram 20 is fitted with a vibrator 21 which permits the ram to be shaken whilst it applies compacting pressure to the concrete mix that has been filled into the form 10.

One side of the form 10 the table 12 is surmounted by a hopper 24 for holding a concrete mix. The bottom of the hopper 24 extends into a chamber 26 which can be divided from the upper part of the hopper by laterally withdrawable sharp'edged separating blades 25 and which is adapted to deliver prescribed volumes of the concrete mix. The bottom of the chamber 26 is closable by a laterally withdrawable slide 28. The walls 27 of the chamber 26 are of telescopic construction only schematically shown in the drawing, so that the volumetric capacity of the chamber can be varied as may be desired.

On the rails 14 a filling box 30 which is fitted with wheels 32 is traversible along the length of the table 12. The box 30 substantially consists of a rectangular frame made of vertical sheet metal panels 31, 33 (cf. FIG.6) so disposed that their bottom edges make sliding contact with the table top when the box 30 traverses the length of the table.

The box 30 is divided into three sections. The center section is bounded by two sheet metal plates 36, 38 which extend across the direction of travel. This section is funnel-shaped due to the panels 36, 38, as shown more particularly in FIG.7, converging from their upper edges towards the centre of the box. The bottom edges of the two plates clear the top of the table 12. Suspended between the two sheet metal plates 36, 38 is a grid formed by longitudinal and transverse intersecting sheet metal strips 40, 41 These elements also clear the table top but the transverse sheet metal strips 40 descend into closer proximity with the table, as shown in FIGS. 7 and 8. The grid formed by these strips 40, 41 serves for initiating the distribution of the concrete mix when the filling box is being charged from the hopper 24, as well as for facilitating the distributed discharge of the mix from the box into the compartments of the form. However. in principle the grid fon'ned by these strips 40, 41 need not conform with the subdivision of the form into compartments.

The two end sections of the filling box 30 contain deflecting plates 42 and 44. During traverse of the box the bottom edges of these deflecting plates slide on the table top, as will be understood from FIGS. 7 and 8. The deflecting plates are set in the form of a Vee and the Vees in the two end sections are substantially parallel. The purpose of these plates is to deflect that part of the concrete mix which in the traversing box is not pushed along by the plates 36 or 38 and to displace this part of the mix in a direction across the direction of travel of the box 34. The plates 44 in one end section of the box gather the mix that has remained on the table 12 and push it inwards towards the center, whereas the plates 42 in the section at the opposite end displace the concrete mix outwards when the box 30 moves to the left in FIG. 1.

Triangular sheet metal tabs 45 affixed to the deflecting surface of the plate 44 fonn angles which align with the longitudinal rows of compartments in the form. Corresponding tabs 43 are formed on the deflecting surface of the other plate 42. The manner in which this arrangement functions will be later described.

Conveniently the deflecting plates 42, 44 are removable insertions. For this purpose the end walls of the filling box 30 are provided with guide means 48 and 50 which are shown in FIG. 6. These guide means have the form of vertical rails or slideways of L- or T shaped cross section. The deflecting plates 42 and 44 are affixed to supporting webs which are provided with slots 49 and 51 (FIG. 9) suitable shaped to fit and engage the guide means 48 and 50.

Instead of V-shaped deflectors 42, 44, straight obliquely placed aprons 60, 62, as illustrated in FIG. 10, might also be used. These aprons would then sweep the concrete mix to one side during a traverse of the box in one direction and to the opposite side during the return traverse of the box. Furthermore, instead of the deflecting insertions illustrated in FIGS. 9 and 10, deflecting devices each resembling a ploughshare might be provided, each connected at the vertex by a joint to a screw shaft extending centrally along the length of the box and rotatably mounted in the two end walls. Rotation of the screw shaft would thus permit the angle of the ploughshares to be varied and adapted to the nature and consistency of the concrete mix or other heterogeneous raw material, the angle at which the ploughshares are set determining the distance of sideways displacement of the mix.

The manner in which the proposed equipment functions will be understood from FIGS. 1 to 5 of the drawings. FIG. 1 shows the equipment after a metered volume of mix has been discharged from the feed chamber 26 under the hopper 24 into the center section of the filling box 30. R indicates residues of material that have remained in the box from a preceding casting operation. The volume of this residue R always remains substantially the same since the capacity of the feed chamber 26 has been set to discharge into the box 30 the correct volume of concrete mix needed for filling the form 10.

Double-acting hydraulic ram cylinders 34 of which the ram pistons are connected to the leading end of the filling box 30 advance the box over the form 10 as shown in FIGS. 20 and 2b. During this stage a residual portion R of concrete mix will collect in the rear section of the box. The box is now rapidly reciprocated above the form 10, as indicated by the doubleheaded arrow 70, but the amplitude of this reciprocation is only a fraction of the overall length of the form in the direction of travel of the box. During this reciprocation the sloping plates 36 and 38 primarily take effect. Since the first compartments of the form 10 to be filled are those nearest the hopper 24, as is the case in conventional equipment, it may be desirable to reciprocate the filling box 30 about a center which is slightly to the left of the center of the form 10 in FIGS. 1 to 5.

Following this short reciprocatory shaking motion the filling box 30 is retracted into starting position as shown in FIGS. 30 and b. This causes the residual portions R of mix that have remained in the box to enter the leading section of the box where they will principally collect in the angles formed by the triangular sheet metal tabs 45. Part of the concrete mix that had been discharged into the box from the feeding chamber 24 will also remain in the center section of the box. The box 36 is now traversed from the position shown in FIGS. 3a and 3b completely across the form into the position illustrated in FIGS. 4a and 4b. The residual portions of concrete mix which in FIGS had been in the leading section of the box will now collect in the trailing section. This is likewise shown in FIG. 4. However, most of the concrete mix retained in the center section will by now have dropped into the compartments of the form 10. In order to assist this process of distribution, the carriage is vibrated by the vibrator 18 before it is transferred from the position in FIG. 3 into that in FIG. 4. During the following return from the position in FIG. 4 into the position in FIG. 5, the major part of the concrete mix in the trailing section will also be distributed between those compartments of the form that are traversed first during the return. These are the compartments that are furthest away from the hopper 24, and which are the most remote from the initial starting position of the box.

In each casting operation, the form I0 is filled to its upper edge. Since a small surplus of concrete mix always remains in the box, as indicated by R in FIG. 4, this object will in every case be achieved. The dotted outline 72 in FIG. 5a is intended to indicate that the capacity of the feeding chamber is exactly equal to the capacity of the form 10. Despite careful preadjustment of the feeding chamber, slight deviations may nevertheless occur because, although the macrostructure of the concrete mix in bulk may be homogeneous, it does contain local inhomogeneities. Any such minor differences are made good by the store of residual mix R.

In order to ensure that the compartments of the form will all be filled to exactly the same level, the proposed method includes removing any excess from the form during the process of compaction. For this purpose the individual compacting plates 120 of the ram 20, which correspond to the several compartments of the form, are each provided with at least one downward extension 150, as shown for instance in FIGS. Ila and 11b. This extension 150 is open at both ends, at the top and at the bottom. Internally it is shaped like a venturi nozzle since the cross section first converges from above downwards and forms a throat 174 from which it diverges again, the bottom end 172 forming a sharp edge. Externally the extension 150 conically gently converges to this sharp edge I72. The throat at 174 is below the level of the compacting plate 120. The height ofthe extension 150 and the cross section of the internal opening at the throat I74 exceeds the diameter of the largest grain size in the concrete mix.

FIGS. l2, l3 and I4 are other embodiments of this device for abstracting excess mix. The extension 150a in FIGS. to I2t is provided with a crescent-shaped recess 152 cut into its bottom edge. To some extent this enables portions of concrete mix situated adjacent the extension 150a during the process of compaction to enter the extension. This arrangement may suggest itselfwhen the cross section of the extension, as indicated in FIG. 12a, differs from the internal cross section of the compartment in the form. FIG. 12a as well as FIG. 110 are views of the extensions from underneath, whereas FIGS. I2!) and 12c are side views in relatively perpendicular directions. The side walls of the extension in FIG. 12b are parallel in one direction, as shown in FIG. 12b, whereas in the other direction, as shown in FIG. 120, the extension downwardly tapers. However, in this embodiment a vertical section of the extension 150a will substantially resemble that of the extension 150 shown in FIG. 11b. The internal cross section of the extension converges upwards from the bottom edge to a throat which is still below the level of the compacting plate 120a, and then diverges again.

The same applies to the extension 150)) shown in FIGS. 13a and 13b which are views corresponding to those in FIGS. 12a and 12b. However, in this instance the extension ISO!) is square in plan and slightly tapers to its bottom end like a truncated pyramid.

FIGS. [40 and 14b are again views corresponding to those in FIGS. 12a and 12c of another embodiment of an extension I50c. This extension 1500 is intended for cooperation with elongated compartments in the form. It comprises internal reinforcing transverse webs 154 which also assist in retaining the portion of concrete mix that is cut out of the surface of the mix contained in the fonn and in preventing this from dropping out whilst it is in course of being lified out. The extension l50c likewise has a downward taper which can be seen in FIG. 14b. If this extension 150c were viewed for instance from the left hand side in FIG.l4b its shape would be that shown in FIG.l3b. This extension 1500 may also be provided with crescent-shaped cutouts l52c, as illustratively shown in FlG.l4b.

The cross section of the opening in the extension 150 respectively 150a or 1501: or l50c should be about one-tenth to one-fourth of the surface area of the compacting plate 120. Good results are achieved if the ration is one-sixth. The minimum internal cross section is determined by the grain size of the mix. The maximum internal cross section depends upon the ability of the mix to maintain an arch inside the cross section. For larger compartments in the fonn more than one such extension may be provided.

When the form has been filled the compacting ram 20 is lowered onto the form 10 until the compacting plates press firmly against the surface of the concrete mix in the several compartments. Each plate 120, as illustrated in FIGS. 15 I9, is affixed to rods 12] attached to the crosshead of the compacting ram 20, which is secured to the end of the piston rod of the hydraulic ram cylinder 22. There is therefore a free space which is open on every side above each compacting plate 120.

FIG.l5 shows the descent of a compacting plate 120, as indicated by an arrow placed alongside the plate. In FIG. 16 the compacting plate 120 has descended into contact with the surface of the concrete mix inside a compartment of the form. The load on the ram 20, possibly assisted by vibration generated by devices 21 or 18 causes the compacting plate 120 to penetrate into the compartment as indicated in FIG. 17. The extension simultaneously cuts into the concrete mix. The pressure and possibly also the effect of simultaneous vibration cause excess mix to enter and pass through the throat 174 in the extension 150 as shown in FIG. I7. The cross section of the throat 174 and the height of the extension 150 are so chosen that they both exceed the grain size of the aggregate used for preparing the mix. This grain size is not shown in the drawing. For the sake of clarity larger particles are shown in the composition of the mix. However, FIG.I8 will show that the excess mix which has passed through the throat 714 will be lifted by the extension 150 when the compacting plate 120 ascends, leaving a substantially frustrumshaped recess in the surface of the mix. The material that has been lifted out by the extension 150 drops out again through the throat 174, as shown in FIG.I9, when during the next filling operation the ram 20 is briefly vibrated.

The proposed method and the equipment for performing the method according to the invention have been more specifically described in their application to concrete. How ever, it will be understood that any material other than concrete but similarly composed of heterogeneous particles could be handled and processed in the same way as described.

What we claim is:

1. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station situated on one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into the form through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for extracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, the filling part of the box being bounded by substantially vertical walls of which the two side walls are parallel to the direction of travel of the box, the two end walls in plan being each in two portions inclined symmetrically to the longitudinal axis of the box, the two portions of each end wall forming a dihedral angle, the dihedral angles of both end walls opening in the same direction.

2. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station on one one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into the form through its open bottom, means being provided in the region of the fonn for compacting the concrete mix inside the form and for extracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, the filling box being divided into three sections of which the center section comprises a funnel which downwardly ends with clearance above the table top, the sections at each end of the box having deflecting plates in sliding contact with the table top, and a grid which is rigidly secured in the funnel and which is comprised by vertical sheet metal strips extending lengthwise and crosswise of the box clear of the table top, the crosswise sheet metal strips extending farther downward than the lengthwise sheet metal strips,

3. Apparatus as claimed in claim 1, the end walls of the filling part of the box comprising defecting devices comprised by rigid panels extending at an angle to the direction of travel of the box in a plane that is substantially perpendicular to the table top, said end walls having bottom edges in sliding contact with the table top.

4 Apparatus as claimed in claim 3, the deflecting devices being sheet metal plates loosely insertable into the box and having holding members which easily fit into and engage correspondingly shaped guide means on the walls of the box.

5. ln apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station situated on one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into the form through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for abstracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, the filling box being divided into three sections of which the center section comprises a funnel which downwardly ends with clearance above the table top, the sections at each end of the box having deflecting plates in sliding contact with the table top, the bottom ends of the deflecting plates having relatively angularly disposed, substantially vertical sheet metal tabs, the vertices of the angles between the tabs and the deflecting plates being in alignment with the rows of compartments in the form.

6. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station situated on one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into the fonn through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for extracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the len of said box, and a ram movable vertical] above the form, t e ram having a pressing surface subdivi ed in conformity with the subdivisions of the form and consisting of a plurality of compacting plates each fitted with means for the reception of excess material in the compartments, each compacting plate having a downward extension which has an opening in its bottom end communicating with a space above, said extension tapering downwardly like a truncated cone and the thickness of the walls of the truncated cone tapering in the downward direction.

7. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station situated on one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiv ing the metered volume of concrete mix through its open top and dropping the mix into the form through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for extracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, and a ram movable vertically above the form, the ram having a pressing surface subdivided in conformity with the subdivisions of the form and consisting of a plurality of compacting plates each fitted with means for the reception of excess material in the compartments, each compacting plate having a downward extension which has an opening in its bottom end communicating with a space above, the cross section of the opening in the extension converging from a bottom sharp-edged end of the extension to a throat located below the level of the compacting plate and then diverging again in the upward direction. 

1. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station situated on one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into the form through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for extracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, the filling part of the box being bounded by substantially vertical walls of which the two side walls are parallel to the direction of travel of the box, the two end walls in plan being each in two portions inclined symmetrically to the longitudinal axis of the box, the two portions of each end wall forming a dihedral angle, the dihedral angles of both end walls opening in the same direction.
 2. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station on one one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into thE form through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for extracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, the filling box being divided into three sections of which the center section comprises a funnel which downwardly ends with clearance above the table top, the sections at each end of the box having deflecting plates in sliding contact with the table top, and a grid which is rigidly secured in the funnel and which is comprised by vertical sheet metal strips extending lengthwise and crosswise of the box clear of the table top, the crosswise sheet metal strips extending farther downward than the lengthwise sheet metal strips.
 3. Apparatus as claimed in claim 1, the end walls of the filling part of the box comprising defecting devices comprised by rigid panels extending at an angle to the direction of travel of the box in a plane that is substantially perpendicular to the table top, said end walls having bottom edges in sliding contact with the table top.
 4. Apparatus as claimed in claim 3, the deflecting devices being sheet metal plates loosely insertable into the box and having holding members which easily fit into and engage correspondingly shaped guide means on the walls of the box.
 5. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station situated on one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into the form through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for abstracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, the filling box being divided into three sections of which the center section comprises a funnel which downwardly ends with clearance above the table top, the sections at each end of the box having deflecting plates in sliding contact with the table top, the bottom ends of the deflecting plates having relatively angularly disposed, substantially vertical sheet metal tabs, the vertices of the angles between the tabs and the deflecting plates being in alignment with the rows of compartments in the form.
 6. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station situated on one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into the form through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for extracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, and a ram movable vertically above the form, the ram having a pressing surface subdivided in conformity with the subdivisions of the form and consisting of a plurality of compacting plates each fitted with means for the reception of excess material in the compartments, each compacting plate having a downward extension which has an opening in its bottom end communicating with a space above, said extension tapering downwardly like a truncated cone and the thickness of the walls of the truncated cone tapering in the downward direction.
 7. In apparatus for producing precast concrete elements in an open-top form divided into a plurality of separate compartments which are filled with a previously exactly metered volume of concrete mix obtained from a feeding station situated on one side of the form, and entrained by a filling box adapted to traverse a horizontal table, said filling box receiving the metered volume of concrete mix through its open top and dropping the mix into the form through its open bottom, means being provided in the region of the form for compacting the concrete mix inside the form and for extracting any excess mix from the form; the improvement in which the table and the track of said box extend beyond said form by at least the length of said box, and a ram movable vertically above the form, the ram having a pressing surface subdivided in conformity with the subdivisions of the form and consisting of a plurality of compacting plates each fitted with means for the reception of excess material in the compartments, each compacting plate having a downward extension which has an opening in its bottom end communicating with a space above, the cross section of the opening in the extension converging from a bottom sharp-edged end of the extension to a throat located below the level of the compacting plate and then diverging again in the upward direction. 